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Old 10-02-2018, 06:09 AM   #1
ABCEDERWALL
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Angry 1972 Chevy Blazer Ignition Switch Smoking

So I have a problem. Just picked up 72 blazer with stick 350 and has the gauge cluster no tach, not the idiot light cluster. My temp gauge and my ammeter gauge currently do not work. Everything else works fine. Iíve spent the last 2 weekends troubleshooting the 2 gauges and am striking out!

For my temp gauge, my dark green wire goes from gauge cluster harness connector all the way to the temp sensor sending unit on the cylinder block as it should. Replaced the sending unit and still doesnít work?

For my ammeter gauge, there is a black wire and a black/white wire that both run from the gauge cluster harness connector to the engin compartment. The black/white wire connects to the red wire running to the battery and has a soldered in-line 4 amp fuse. The fuse is good. The black wire runs to the positive battery terminal. My ammeter gauge stays smack dab in the middle and doesnít move, even with the battery disconnected?

The 3rd problem I have is tonight when I get as laying on the floorboard and looking up under the dash, I was turning the key on and noticed smoke bellowing out of my key ignition switch housing! So, I disconnected the battery and removed my key ignition switch and took it apart to see what the smoke was coming from. It looks like the metal leg that the ACC (Big brown wire and little brown with white wire) and the SOL (big purple wire) connect to melted in half? What would cause this??
Any help would be much appreciated!!

Here are pictures:
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Old 10-03-2018, 02:47 AM   #2
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Re: 1972 Chevy Blazer Ignition Switch Smoking

OK, so I really need some help here... I'm hoping someone will reply to my post soon with some solid advise... I sketched a drawing with color showing my current wiring setup for my ignition system. From what I can decipher, my wiring is correct? I do have one question though on my current setup?? I noticed that the PURPLE wire running from the "S" position on the starter solenoid to the "SOL" position in the ignition switch is not showing up on any electrical diagrams I have come across? Is this proper for my setup or is it wrong? I appreciate any feedback you can give!!
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Old 10-03-2018, 11:00 AM   #3
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Re: 1972 Chevy Blazer Ignition Switch Smoking

I had this problem before with a newer harness but the original ignition switch. I just bought a new switch and no problems since. The purple wire does go from the S terminal to the SOL on the switch but, normally goes thru the fuse panel with in its travel. Does yours? Based on your picture it doesn't...
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Old 10-03-2018, 01:36 PM   #4
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Re: 1972 Chevy Blazer Ignition Switch Smoking

wiring diagrams...http://67-72chevytrucks.com/vboard/s...d.php?t=185856
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Old 10-04-2018, 01:47 AM   #5
ABCEDERWALL
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Re: 1972 Chevy Blazer Ignition Switch Smoking

Sorry 6768chevylover!! My artist skills are sub-par, and it took a lot for me to even post that drawing ... My drawing is incorrect only for the large purple going from SOL on ignition switch to the S on the starter solenoid. It actually does go through the bulkhead connector on the firewall and into the engine bay like it should. See the picture attached. Thank you for your input. I'm wondering if it was just a coincidence in timing that I was investigation my electrical under the dash at the same time my ignition switch went out?? I bought a new switch and installed it, just haven't connected battery yet as I'm worried It's gonna fry the new one!!
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Old 10-04-2018, 01:50 AM   #6
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Re: 1972 Chevy Blazer Ignition Switch Smoking

Thanks for the reply A1971Blazer! I have those diagrams already, but I noticed there are some wires that don't match my vehicle's setup?
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Old 10-04-2018, 01:58 AM   #7
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Re: 1972 Chevy Blazer Ignition Switch Smoking

So I have 3 wires that run from a voltage regulator or something above my fuse block inside the cab, and run wrapped together through the firewall into the engine compartment, and are all cut? Does anyone know what they used to run/connect to?? See picture:
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Old 10-04-2018, 02:06 AM   #8
ABCEDERWALL
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Re: 1972 Chevy Blazer Ignition Switch Smoking

Here's a picture of the 3 wires that are cut in engine bay. This picture is of the other end of the wires plugged into some sort of regulator or something above the fuse block... Any one know what these used to connect to??
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Old 10-04-2018, 02:16 AM   #9
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Re: 1972 Chevy Blazer Ignition Switch Smoking

Horn relay. Is it bolted to the firewall? Have had trouble with my old wiring in this area, what with the relay getting super hot and melting wires. Still trying to figure it out also.
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Old 10-04-2018, 02:20 AM   #10
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Re: 1972 Chevy Blazer Ignition Switch Smoking

Oh, just noticed your firewall may be fiberglass? Patched or what? Might be a ground problem as it is not attached to a metal surface.
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Old 10-04-2018, 02:34 AM   #11
ABCEDERWALL
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Re: 1972 Chevy Blazer Ignition Switch Smoking

Thanks for reply swyfor5! Yes it is attached to the metal firewall. That fiberglass you are seeing is the underlayment with a ton of dust and paint overspray on it. So if that's the horn relay that those wires are connected to, where do they run in the engine compartment? My horn only has 1 prong for a wire to plug into and that wire is already properly there? Also, the horn works??

Last edited by ABCEDERWALL; 10-04-2018 at 02:46 AM.
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Old 10-04-2018, 03:28 AM   #12
ABCEDERWALL
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Re: 1972 Chevy Blazer Ignition Switch Smoking

double checking all of my electrical... does anyone know why the inline fuses that are on the wires 1 & 12 running from the dash cluster connector to the battery (black w/white wire and the black wire) require 4 amp SHORT fuses?? I found the one on the black w/white wire, but I cant find the one on the black wire? I'm assuming I need to add one? Currently my stock ammeter gauge doesn't work, and this is the only thing that I see missing?? Any input would be appreciated??!! I have a gauge cluster, not dummy light set up...
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